Consideration of Inner and Outer Phase Configuration in Tube Radial Distribution Phenomenon Based on Viscous Dissipation in a Microfluidic Flow Using Various Types of Mixed Solvent Solutions.

When mixed solvent solutions, such as ternary water-hydrophilic/hydrophobic organic solvents, water-surfactant, and water-ionic liquid, are delivered into a microspace under laminar flow conditions, the solvent molecules radially distribute in the microspace, generating inner and outer phases. This specific fluidic behavior is termed "tube radial distribution phenomenon", and has been used in separation technologies such as chromatography and extraction. The factors influencing the configuration of the inner and outer phases in "tube radial distribution phenomenon" using the above-mentioned mixed solvent solutions were considered from the viewpoint of viscous dissipation in fluidic flows. When the difference in the viscosity between the two phases was large (approximately >0.73 mPa·s), the phase with the higher viscosity formed as an inner phase regardless of the volume ratio. The distribution pattern of the solvents was supported by the viscous dissipation principle. Contrarily, when the difference was small (approximately <0.49 mPa·s), the phase with the larger volume formed as the inner phase. The distribution pattern of the solvents did not always correspond to the viscous dissipation principle. The current findings are expected to be useful in analytical science including microflow analysis research.

Separation of Metal Complexes with Counter Ions by Tube Radial Distribution Chromatography Using a Ternary Solvent Containing 8-quinolinol.

An open-tubular capillary chromatography system (tube radial distribution chromatography, TRDC) was developed using a ternary solvent (water-acetonitrile-ethyl acetate; volume ratio, 3:8:4) containing 10 mmol L(-1) 8-quinolinol for the separation of nitrate, chloride, and sulfate compounds of Ni(II), Al(III), and Fe(III). When a mixed solution of the Ni(II) compounds was injected into an untreated fused-silica capillary tube (90 cm × 75 µm i.d.) with a ternary solvent flow rate of 0.8 µL min(-1), the compounds were eluted in the following order: [Ni(II)-(8-quinolinol)3] complex, [Ni(II)-(8-quinolinol)]-nitrate ion interaction complex, [Ni(II)-(8-quinolinol)]-chloride ion interaction complex, and [Ni(II)-(8-quinolinol)]-sulfate ion interaction complex. The elution of mixtures of the Al(III) and Fe(III) compounds showed similar trends.

Investigation of inner and outer phase formation in tube radial distribution phenomenon using various types of mixed solvent solutions.

When mixed solvent solutions, such as ternary water-hydrophilic/hydrophobic organic solvents, water-surfactant, water-ionic liquid, and fluorous-organic solvents are delivered into a microspace under laminar flow conditions, the solvent molecules are radially distributed in the microspace, generating inner and outer phases. This specific fluidic behavior is termed "tube radial distribution phenomenon" (TRDP). In this study, the factors influencing the formation of inner and outer phases in the TRDP using the above-mentioned mixed solvent solutions were investigated. We examined phase diagrams, viscosities of the two phases (upper and lower phases in a batch vessel), volume ratios of the phases, and bright-light or fluorescence photographs of the TRDP. When the difference in viscosities between the two phases was large (> approximately 0.73 mPa·s), the phase with the larger viscosity formed an inner phase regardless of the volume ratios, whereas when the difference was small (< approximately 0.42 mPa·s), the phase with the larger volume formed an inner phase. The TRDP using a water-surfactant mixed solution was also investigated in capillary chromatography based on TRDP.

Investigations into tie lines and solubility curves on phase diagrams in open-tubular capillary chromatography using ternary mixed-carrier solvents.

Open-tubular capillary chromatography using a ternary solvent mixture consisting of a water-hydrophilic-hydrophobic organic solvent as a carrier solution has been developed. When the ternary carrier solution is fed into the capillary tube, the carrier solvents are radially distributed and generate inner and outer phases in the tube. The outer phase functions as a pseudo-stationary phase in chromatography. In this study, investigations proceeded with reference to the tie lines and solubility curves on the phase diagram of the ternary mixed solvents. Model analytes, 1-naphthol and 2,6-naphthalenedisulfonic acid, were separated in this order with ternary water-acetonitrile-ethyl acetate solvent mixtures (organic solvent-rich solutions) that possessed various solvent compositions on the tie lines. In addition, fluorescence photographs of the dyes dissolved in the ternary solvents in the capillary tubes were observed with a fluorescence microscope-CCD camera system. It was found that the separation performance on the chromatograms and the phase formation observed in the fluorescence photographs were related to data provided through the tie lines and solubility curves on the phase diagram. The solvent compositions on the same tie line that gave different volume ratios of upper and lower phases in a vessel influenced the chromatographic separation, or the resolutions of the analytes, and also the inner and outer phase formation in the chromatography.

Elution behavior of lambda-DNA with ternary mixed carrier solvents in an open-tubular capillary under laminar flow conditions.

An open-tubular capillary chromatography was developed based on the tube radial distribution of the ternary mixed carrier solvents that generated the inner and outer phases under laminar flow conditions. This is called "tube radial distribution chromatography" (TRDC). In this report, the elution behavior of lambda-DNA (48502 bp) as a biopolymer was examined by the TRDC system. The ternary mixture of water-acetonitrile-ethyl acetate, 15:3:2 or 3:8:4 volume ratio, as a carrier solution was fed into the capillary tube made of polytetrafluoroethylene (PTFE) or fused-silica. The mixture of hydrophobic 1-naphthol and hydrophilic lambda-DNA was subjected to the TRDC system using the water-rich carrier solution. Lambda-DNA and 1-naphthol were distributed between the inner and outer phases due to their hydrophilic and hydrophobic nature, and then eluted in this order, undergoing chromatographic separation. The mixture of hydrophilic 2,6-naphthalenedisulfonic acid and hydrophobic lambda-DNA that was treated with surfactants was also examined with the organic solvent-rich carrier solution. The modified hydrophobic DNA and 2,6-naphthalenedisulfonic acid were distributed and eluted in this order due to their nature.

Use of tube radial distribution of ternary mixed carrier solvents for introduction of absorption reagent for metal ion separation and online detection into capillary.

When ternary mixed solvents consisting of water-hydrophilic/hydrophobic organic solvents are fed into a micro-space under laminar flow conditions, the solvent molecules are radially distributed in the micro-space. The specific fluidic behavior of the solvents is called the "tube radial distribution phenomenon (TRDP)". A novel capillary chromatography method was developed based on the TRDP that creates the inner major and outer minor phases in a tube, where the outer phase acts as a pseudo-stationary phase. This is called "tube radial distribution chromatography (TRDC)". In this study, Chrome Azurol S as an absorption reagent was introduced into the TRDC system for metal ion separation and online detection. The fused-silica capillary tube (75 µm id and 110 cm length) and water-acetonitrile-ethyl acetate mixture (3:8:4 volume ratio) including 20 mM Chrome Azurol S as a carrier solution were used. Metal ions, i.e. Co(II), Cu(II), Ni(II), Al(III), and Fe(III), as models were injected into the present TRDC system. Characteristic individual absorption characteristics and elution times were obtained as the result of complex formation between the metal ions and Chrome Azurol S in the water-acetonitrile-ethyl acetate mixture solution. The elution times of the metal ions were examined based on their absorption behavior; Co(II), Ni(II), Al(III), Fe(III), and Cu(II) were eluted in this order over the elution times of 4.7-6.8 min. The elution orders were determined from the molar ratios of metal ion to Chrome Azurol S and Irving-Williams series for bivalent metal ions.